If to make a summary of a good number of MSDS that I could find at Shell Europe sites, then Helix Ultra base stock is:
5W-40 ........... gr. III (or gr.II+ ?)
5W-30 ........... PAO + gr III (or PAO + gr.II+ ?)
5W-30 AB ...... gr.III
5W-30 diesel .. gr.III + PAO + Esters
0W-40 ........... PAO
10W-60 ......... 1). PAO, 2). Esters + PAO
Thus, Helix Ultra base stocks may differ from country to country and even used gr. III is not everywhere the same: looks like hydrogen processing of mineral oils are made at different levels. I made this conclusion based on MSDS of Norwegian, Swedish and Dutch origin.
I start to doubt whether it would be fair to consider mineral oils after described treatments as hydrockracked oil (Shell XHVI oils). Some of descriptions resemble more to gr.II+. May be I am mistaken, but according to a.m. MSDS:
Norway
5W-40: Hoyraffinert Mineralolje (n.b.:same as Helix Plus 10W-40 and Helip Plus S 5W-40
5W-30: Polyalfaolefiner 30-60 %, Hoyraffinert Mineralolje 5-10 %
5W-30 AB: Hyrdogenbehandlet Rest Vorks 60-100 %
Netherlands:
Helix Ultra 5W-30/40: Synthetische olie
Helix Ultra 5W-30 Diesel: Mengsel van intensief met waterstof behandelde slackwax, synthetische esters, polyolefinen
Helix Plus 10W-40: Mengsel van geraffineerde mineral olie intensief met waterstof bahandelde slackwax
Sweden:
Helix Ultra 5W-40 - something similar to Dutch Helix Plus 10W-40.
http://www3.shell.no/op/hmschess/chess/html/grp_4/dir.htm
http://www.shell-tic.com/index.cfm?fuseaction=home.main